Donaldson Mountain stands within the watershed of the Raquette River, which drains into the Saint Lawrence River in Canada, and into the Gulf of Saint Lawrence. The southeast side of Donaldson Mt. drains into Seward Brook, thence into the Cold River, a tributary of the Raquette River. The southwest end of Donaldson Mt. drains into Boulder Brook, thence into the Cold River. The northwest side of Donaldson drains into Calkins Brook, thence into the Raquette River.